Seal

ABSTRACT

This invention provides a seal for closing an entry or exit aperture of an apparatus in which a moving strip of material is to be treated while in either a partial vacuum or while in a pressurized container, the seal serving completely to close the entry or exit aperture periodically and to deform as the material under treatment moves so that no appreciable drag is imparted to the material and then to open slightly to allow the seal to become undeformed before closing again upon the material so that the increments of time for which the seal is open are small and thus passage of fluid across the seal is minimized thereby to enable the required degree of vacuum or pressure to be maintained without imposing undue stress upon the mechanism used to create the vacuum or pressure conditions required.

United States Patent n 1 Sedwell 1 SEAL [75] Inventor: Alfred JamesSedwell, Bury, En-

gland [73] Assignee: General Engineering Company (Radcliffe) Limited[22] Filed: Aug. 3, 1971 [21] Appl. No.2 168,609

[30] Foreign Application Priority Data 3,544,388 12/1970 Russell..1l8/405 Primary Examiner-Joseph R. Leclair Assistant ExaminerRobert 1.Smith Attorney-Salter & Michaelson [57] ABSTRACT This invention providesa seal for closing an entry or exit aperture of an apparatus in which amoving strip of material is to be treated while in either a partialvacuum or while in a pressurized container, the seal serving completelyto close the entry or exit aperture periodically and to deform as thematerial under treatment moves so that no appreciable drag is impartedto the material and then to open slightly to allow the seal to becomeundeformed before closing again upon the material so that the incrementsof time for which the seal is open are small and thus passage of fluidacross the seal is minimized thereby to enable the required degree ofvacuum or pressure to be maintained without imposing undue stress uponthe mechanism used to create the vacuum or pressure conditions required.

9 Claims, 5 Drawing Figures Patented March 27, 1973 2 Sheets-Sheet lINVENTOR:

ALFRED JAMES SEDWELL BY SALTER & MICHAELSON,

Attorneys.

Patented March 27, 1973' 2 Sheets-Sheet 2 INVE'NTOR:

. ALFRED JAMES SEDWELL SALTI'IR & MICHAELSON,

v SEAL This invention concerns an improved seal, and particularly thoughnot exclusively a seal adapted for use it is known to provide at theinlet and outlet of a vacuum treatment chamber a series of seals whichserve effectively to incrementally reduce the pressure from atmosphericto a vacuum of the order Torr within the treatment chamber. In such anarrangement of seals it has been the practice to use precision machinedelements for producing the seals and whilst such sealing arrangementsare capable of being used in an effective manner they possess certaininherent disadvantages. One disadvantage lies in the fact that the sealsare expensive to produce and despite the care with which they are madethey haveinherent leak paths thus making it necessary to employ highcapacity pumping equipment to compensate for the leakage between theseal elements and the material to be treated. Since high capacitypumping equipment is used the capital cost of the equipment is high asin fact is the running and maintenance cost.

It has recently been proposed to use a sealing arrangement whichbasically relies upon the use of a se-' ries of columns of particulatematerial for creating the seals and thus is considered to beadvantageous since the cost of producing the seals is thought not to beas high as heretofore-since'the need to produceseal elements to closemachining tolerances is eliminated or at least substantially reduced. Itis also thought that, due to the effectiveness of sealing achieved bythe use of equipment can be lower whilst still achieving the desireddegree of vacuum and thus the capital cost of equipment should becapable of being reduced. 7

The applicant have now appreciatedthat if the entry and exit aperturesfor material to be processed can be completely closed for periods oftime duringthe feeding of material through the apparatus an even moreefficient sealing arrangement will result. Such-a-sealing arrangement isthought to be most advantageous if-employed at the outermost of theentry and exit series of seals although it may also be used additionallyat other positions in each series of seals.

The principal object of the present invention is to provide a sealarrangement in which the seal entry can be, in conjunction with thematerial to be processed, completely closed during passage of the amaterial through the apparatus.

According to the present invention a seal is characterized in that itincludes relatively moveable opposed shutters, each having in its edgeregion adapted to lie adjacent a material to be processed a deformableelement adapted to be placed in contact with the material to beprocessed, there being means associated with at least one of theshutters whereby it may be caused sequentially to move towards and awayfrom the other shutter to remain in close proximity thereto until thelimit of deformation of the deformable element has been reached and thento be moved away from the other shutter foraperiod of time sufficient toallow recovery of the deformable element to its original position priorto being moved again towards the other shutter.

particulate material, the capacity of the pumping 3 Preferably both ofthe shutters are associated with means adapted to cause sequentialmovement.

In one form of apparatus the means adapted to cause movement of theshutters includes electrical or electronic equipment adapted to producea square wave output signal, the latter being adapted to cause saidshutter movements.

The invention will now be described further, by way of example only,with reference to the accompanying diagrammatic illustrations, in which:

FIG. 1 is a diagrammatic illustration of a seal made in accordance withthe invention;

FIG. 2 is a representation of an electrical wave form produced by anapparatus arranged to control seal movements;

FIGS. 3 and 4 are respectively illustrations of parts of the seal ofFIG. 1 in an open and closed position, and

FIG. 5 is a view similar to FIG. 3 or 4 showing a modification.

In the following description only one seal will be referred to but ofcourse in an apparatus for use in the treatment of material underconditions of vacuum or pressure at least two such seals arecontemplated.

The seal as shown in FIG. 1 includes a housing 10 having therein achamber 11 connected through a conduit 12 to a pumping means (not shown)which, in an apparatus incorporating a vacuum treatment chamber (notshown), is adapted partially to evacuate the seal chamber 11.

In opposed walls 13 of the housing 10 are provided apertures 14 andthrough which material 15 passes to enter the chamber 11 via aperture 14and through which material 15 leavesthe chamber 11 via aperture 1411from a supply reel 16 of material 15. In these walls 13 areprovidedopposed pairs of shutter guides 17, one pair being located at each sideof the housing 10. The shutter guides of a pair 17 are located one ateach side of'the material entry aperture 14. Within each guide 17 is aslideable shutter element 18 having at its free edge,

that is the edge nearest the material entry aperture 14, a flexiblematerial elementl9 preferably-of round cross section and preferably madefrom soft rubber. Other soft deformable but impervious material may beused-in place of rubber.

The'shutters 18 are connected to a means for causing them to move intheir respective guides 17 towards and away from 'each other insynchronism. Conveniently the means for moving the shutters is in theform of a 7 system including an eccentric 20 and link 21.

To operate the eccentric 20 and link 21 there is provided electricalapparatus (not shown) adapted to produce an output signal of squarewaveform as shown in FIG. 2. The peaks 2 2 and. valleys 23'of the wavecorrespond to top and bottom dead center positions of the eccentric 20respectively.

Thus as the signal is emitted the shutters18-will, assuming theminitially to be open (as shown in FIG. 3), move towards each other,remain in a closed position (as shown in FIG. 4) for an increment oftime, and then move apart to remain apart for a further increment oftime.

Now assuming that the apparatus is in use and a strip l5-of material isbeing passed through the seal then initially (again assuming theshutters 18 to be open) the shutters 18 will move towards each othercompletely to close the inlet aperture 14 in the housing 10. As thematerial 15 continues to move-into the chamber 11 in the housing whichis evacuated to a pre-determined degree of vacuum by the pump, theflexible material 19 on the shutter edges will be deformed (as shown inFIG. 4) thus maintaining the seal whilst allowing movement of thematerial 15. Under influence of the square wave signal (as shown in FIG.2) the shutters 18 will, after a short increment of time, move apart toallow the flexible material 19 to return to its original undeformedcondition. The shutters 18 are now again moved to the closed position toseal the inlet aperture 14 completely.

Clearly whilst the shutters 18 are closed onto the material there willbe no leakage path and equally clearly whilst they are open there willbe a leakage path but by arranging for shutter movement to be small'theleakage path may be kept within acceptable dimensions for example it isenvisaged that the gap between the flexible material 19 of the shuttersand the material 15 will not exceed 0.1 inch when the shutters 18 arefully retracted from the material 15 and in fact a gap of 0.05 inch isthought to be obtainable.

The ratio of the time for which the shutters 18 are closed to the timefor which they are open will be dependent upon the wave form and thiscan be modified from the form illustrated in FIG. 2 by the use ofmodulating equipment so that for example the increment of time for whichthe shutters 18 are closed will be greater than the time for which theyare open. The speed at which the material 15 passes through the sealwill be related to the wave form used to operate the shutters 18 in suchmanner that whilst the shutters 18 are closed there will be no slippageof material between the flexible elements 19. This is desirable(particularly at theoutlet seal) to obviate the possibility of damagingor marking a coating put onto the material 15 in the treatbut this willnot, it is thought, have any adverse effect on the material. I

It Will also be apparent that in some cases the chamber 11 will beassociated with a further chamber (indicated in FIG. 1 in broken line)in which the degree of vacuum or pressure is again to be controlled bypumping equipment. The seal between the first and second chambers may infact be common to both chambers and thus seal 14a serves to seal chamber11 from the next chamber. Alternatively seal 14a may be in the form of acolumn of particulate material as recently proposed by the present.

I claim:

1. A seal including at least one pair of relatively movable shutters,deformable edge regions for each of said shutters along adjacent edgesof said shutters, means associated with at least one of the shutters ofthe at least one pair of shutters to cause movement thereofalternatively towards and then away from the other reference to the useof a mechanical means for causing of operation is thought'to bedesirable where the frequency of movement of the shutters 18. is high.

In a modification of the seal described above it is possible as shown inFIG. 5 to provide, at the entry to the chamber 11,- a seal consisting oftwo sets of shutters 18 and 18a. In this case the shutter movements ofone set will be 180 out of phase with the movements of the other set ofshutters so that at no time will there be a gap between the material andthe shutters through which leakage can occur.

It will also be appreciated that whilst reference has been made to theuse of a vacuum pump in association with the chamber 11 it is alsopossible to use the seal in apparatus designed for the processing ofmaterial under conditions of elevated pressure. In such a case thepumping arrangements would be such as to pressurize the chamber 11. g

It is possible to have one of the shutters 18 fixed in position and tomove only the other shutter 18 towards and away from the material. Inthis case slight deviation in the path of movement of the material willtake place shutter of the pair and to retain the shutters in closeproximity with each other for an increment of time so as, in use, tocause the said deformable edge regions of the said shutters to contact amaterial as it is passed through said seal, the said increment of timebeing that taken fully to deform said deformable edge regions of saidshutters, and then to separate the shutters to allow said deformableedges to return to an undeformed condition before they again becomelocated in said close proximity with each other.

2. A seal as set forth in claim 1 in which both shutters of a pair ofshutters are associated with means for caus ing movement thereof.

3. A seal'as setforth in claim 1 in which the means for causing shuttermovement includes electrical apparatus adapted to produce a square waveoutput signal, said signal serving to control said shutter movement.

4. A seal as setforth in claim 1 in which the means for causing shuttermovement includes electrical apparatus adapted to. produce a square waveoutput signal, an eccentric, a linkfroni said eccentric to said shutterand means for causing movement of said eccentric by said output signalfrom said electrical apparatus.

5. A. seal as set forth in claim l in which said deformable edge regionsof said shutters are soft rubber.

6. A seal as set forth in claim 1 in 'which said deformable edge regionsof said shutters are circular in cross-section when undeformed.

7. A seal as set forth in claim 1 in which two pairs of shutters areprovided, said shutters of one pair being movable out of phasewith saidshutters of said other pair; 7

8. A seal as set forth in claim 1 in which said shutters are slidable inslides in a wall of a chamber through which a strip of material is topass, means being provided in association with said chamber to createand maintain a pressure therein different to prevailing atmosphericpressure.

9, A seal as set forth in claim 8 in which said means associated withsaid chamber is adapted to provide and maintain a sub-atmosphericpressurein said chamber.

* l i i t

1. A seal including at least one pair of relatively movable Shutters,deformable edge regions for each of said shutters along adjacent edgesof said shutters, means associated with at least one of the shutters ofthe at least one pair of shutters to cause movement thereofalternatively towards and then away from the other shutter of the pairand to retain the shutters in close proximity with each other for anincrement of time so as, in use, to cause the said deformable edgeregions of the said shutters to contact a material as it is passedthrough said seal, the said increment of time being that taken fully todeform said deformable edge regions of said shutters, and then toseparate the shutters to allow said deformable edges to return to anundeformed condition before they again become located in said closeproximity with each other.
 2. A seal as set forth in claim 1 in whichboth shutters of a pair of shutters are associated with means forcausing movement thereof.
 3. A seal as set forth in claim 1 in which themeans for causing shutter movement includes electrical apparatus adaptedto produce a square wave output signal, said signal serving to controlsaid shutter movement.
 4. A seal as set forth in claim 1 in which themeans for causing shutter movement includes electrical apparatus adaptedto produce a square wave output signal, an eccentric, a link from saideccentric to said shutter and means for causing movement of saideccentric by said output signal from said electrical apparatus.
 5. Aseal as set forth in claim 1 in which said deformable edge regions ofsaid shutters are soft rubber.
 6. A seal as set forth in claim 1 inwhich said deformable edge regions of said shutters are circular incross-section when undeformed.
 7. A seal as set forth in claim 1 inwhich two pairs of shutters are provided, said shutters of one pairbeing movable 180* out of phase with said shutters of said other pair.8. A seal as set forth in claim 1 in which said shutters are slidable inslides in a wall of a chamber through which a strip of material is topass, means being provided in association with said chamber to createand maintain a pressure therein different to prevailing atmosphericpressure.
 9. A seal as set forth in claim 8 in which said meansassociated with said chamber is adapted to provide and maintain asub-atmospheric pressure in said chamber.